RDCs were built for bidirectional operation.  Each end of the car is equipped with a control cab, headlights and horn.  This allows the train to operate in either direction without turning around. 

VIA Rail 6148 began its life as an RDC-5, which means it had no control cabs.  The control cabs were added later when the car was refurbished.  See if you can find at least three differences between the front of 6148 and BC-30.